Research On Magneto-rheological Fluid Squeeze Flow Dynamics And Its Application In Diesel Engine Mounts

Diesel engine is widely used in engineering fields such as automobile.The unbalanced force and torque generated during the working process are the main vibration sources,which seriously affect the system comfort and stability.As the key part of diesel engine vibration isolation components,mounts' performance directly affects the vibration isolation effect.Traditional passive mount can only achieve better vibration isolation effect at a certain frequency range.Semi-active mount can realize better vibtation isolation during the whole frequency domain,with lower energy consumption and cost compared to the active mount.So the development of high-performance semi-active mount has become a research focus in recent years.As a kind of intelligent material which can quickly response,magnetorheological fluid(MRF)has a broad prospect in the field of semi-active systems.The MRF squeeze flow mode,as one of the three kinds of basic work modes,can produce greater responsiveness under the same external excitation.And diesel engine can produce a large exciting force under small amplitude,so developing MRF squeeze mount can make full use of the special properties.The vibration of diesel engine has broadband frequency characteristics,so studying the whole frequency domain's characteristics has the vital significance.However,the MRF squeeze flow mechanism now is not fully clear,lacking research on flow dynamics at high frequency.To achieve the optimal vibration isolation performance,comprehensive research and expression becomes a problem urgently to be solved.This paper will take a comprehensive research on MRF squeeze dynamics;mainly on dynamic characteristics at high frequency.Then develop a kind of MRF squeeze mount,and optimal design the structure using the multi-objective optimization genetic algorithm.Lastly,design the semi-active controller and simulate the vibration control.The main work and conclusions are as follows:1.Modeling of the MRF squeeze dynamicsFirstly,based on fluid mechanics equation,establish the MRF squeeze dynamic model considering the absence and existence of the magnetic field.Reveal the boundary slip's influence law on the MRF squeeze dynamics.Then,based on the navier-stokes equation,establish the MRF squeeze model considering the inertial effect.Reveal the MRF squeeze dynamic mechanism under high frequeny.Lastly,set up the model of boundary pressure and shear-flow force,comprehensively expressing the force produced by the piston motion.2.Experiment research on the MRF squeeze dynamicsFirstly,optimal design a kind of MRF squeeze character test device and conduct the experiment test.Then,get the the excitation frequency,current intensity,initial gap and temperature's effect law on the MRF squeeze dynamics.Lastly,verify the squeeze model with parameter identification.3.Optimal design the MRF squeeze mountFirstly,design the structure of MRF squeeze mount and deduce the model of adjustment coefficient,inertial force and the magnetic response time.Then,using the multi-objective optimization genetic algorithm,optimize the structure parameters.4.Simulink the semi-active vibration control of the diesel engineFirstly,set up 6 degrees of freedom dynamic model of the diesel engine vibration isolation system.Calculate the unbalance vibration force of the diesel engine and optimize the stiffness of mount rubber.Then,adopt LQR theory to Simulink the semi-active vibration control,to reduce the vibration force's transmissibility.Lastly,put up a kind of method to select the weight coefficient,to improve the control effect and save the parameter selection time.